The 2-chlorethylnitrosoureas (CENUs) are clinically important alkylating agents of DNA, but their mechanisms of action are poorly understood. Several alkylguanines have received attention as possible sites of anti-tumor activity but little information is available as to the relative susceptibilities of guanines within DNA. There is evidence from model DNAs, treated with methylating agents, that implies that the sequence around guanine may affact the site and frequency of aklylation of guanine. The purpose of this project is to elucidate what effect the base sequence around a guanine exerts on the formation of specific alkylation products upon exposure of DNA to CENUs. Such information will aid in the understanding of the mechanisms of action of CENUs and assist in the design of more effective drugs. Synthetic polydeoxyribonucleotides of defined sequence, poly(dG)*poly(dC), poly(dG-dC)*poly(dG-dC), poly(dA-dC)*poly(dG-dT), poly(dA-DG)*poly(dC-dT)and DNA will be treated will BCNU, CCNU and methy1-CCNU. The alkylguanines, 7-(B-chloroethyl)guanine, 7-(B-hydroxyethl)guanine, 7-(B-aminoethyl)guanine 06-(B-hydroxyethyl)guanine and 1,2-(diguan-7-yl)ethane, will be separated by reverse-phase H.P.L.C. and quantitated by U.V. absorption. Statistical comparison of the quantities of alkylguanines as a function of base sequence and as a function of alkylating agent will be made. These data will be used 1) to determine which base sequences are more susceptible to certain types of alkylation, 2) to compare the three CENUs for activity toward certain sequences to yield specific products, 3) to examine the data from methyl-CCNU and identify any potential correlation of its products related to base sequence with the drug's leukemogenic nature, and 4) to ascertain what these data reveal about the mechanisms of action of CENUs as a whole.